You can delay the enhancement of an incantation to after you have successfully channeled an incantation.

Benefit: If you successfully channel an incantation with a duration of aura or a duration measured in rounds, you may enhance the incantation at a later time. To do so, you must make a channeling check equal to the enhanced DC – 5. This is an exception to the rule that incantations can’t be enhanced after they are channeled.